Optical properties of linear-chain mercury compounds

Polarized reflectance studies from single-crystal faces of the anisotropic Hg-chain conductor Hg2.86 AsF₆ are presented. The results indicate metallic behavior for electronic excitations along the chains (in the →a-→b plane) with free-electron Drude theory giving a satisfactory initial description of the data. The plasma frequency is found to be ωₚ=4.8 eV and combined with the electron density yields a free-electron optical mass. The implied optical conductivity in the a-b plane at room temperature is σₒₚₜ=(4π)^-1ωₚ²τ10⁴ (Ωcm)^-1 in good agreement with the measured dc value. Normal-incidence studies of reflectance from crystal faces at an angle with the a-b plane are analyzed to provide a complete description of the complex dielectric tensor in the spectral range from 0.5 to 4.2 eV.